Electrical connection for sheathed conductors



y 2, 1967 A. H. FIRESTONE 3,317,656

ELECTRICAL CONNECTION FOR SHEATHED CONDUCTORS Filed May 25, 1964 BY ME.'EQZQA United States Patent 3,317,656 ELECTRICAL CONNECTION FOR SHEATHEDCONDUCTORS Alexander H. Firestone, Pasadena, Calif., assignor toElectro-Optical Systems, Inc., Pasadena, Calif. Filed May 25, 1964, Ser.No. 370,019 2 Claims. (Cl. 174-86) The present invention relates ingeneral to solderless connectors of the type used for joining the endsof electrical conductors to provide an electrically conductive jointtherebetween, and more particularly relates to a novelsleeve-type ofconnector which is adapted to receive the ends of a pair of insulatedconductors and to be crimped to provide a joint that is substantiallywater tight and that has good electrical conductivity.

While the present invention has wider application, it is particularlyadaptable for use with an electric heating device of the sheathed typecomprising a resistor and a sheath enclosing the resistor, the latterbeing electrically insulated from the sheath by suitableelectrical-insulating, heat-conducting means. The invention providesmeans for sealing the ends of heating devices and also provides meansfor electrically connecting the heating device to a source of electricalcurrent, the electrical connection between the terminal of the resistorand the conductor wire being adequately protected against shorting andagainst action of deleterious matter which may be in close relation tothe device.

More particularly, in the usual sheathed-type of heater element, a thinresistive wire is covered with a thin layer of appropriate insulationand the combination protected with a metal tubing or sheath. However,the ends of the heater wire protrude from the sheath and connection ismade to them for the purpose of sending current through the wire. One ofthe troubles with this kind of arrangement is the fact that the ends ofthe heater wire are subject to bending due to vibration or the weight ofattachments to them, with the result that the wire eventually breaks. Inmissile usage, for example, the wire ends experience a great deal ofvibration.

A number of attempts have been made in the past to prevent this fromhappening but the results this far have not been satisfactory. For onething, these prior art devices turned out to be incompatible withoperation in a vacuum and at elevated temperatures. Accordingly, theyproved to be unreliable. For another thing, because of the materials andthe techniques used in the manufacture of these earlier devices, theyturned out to be rather expensive.

Accordingly, it is an object of the present invention to provide anelectrical connector that would function successively in vacuums whenoperated therein at elevated temperatures.

It is another object of the present invention to provide a simple andeffective connector that is operative to produce a joint of goodelectrical conductivity under a wide variety of environmentalconditions.

It is a further object of the present invention to provide a sturdy,reliable and relatively inexpensive electrical connector.

These objects are achieved by means of the electrical connectorencompassed by the present invention. More particularly, a connectoraccording to the present invention is a sleeve-type connector in whichan end of the heater wire is joined, as by crimping, to another wire oflarger diameter. More specifically, the larger wire has a hole bored init for a short distance along its axis and the end of the resistor wireis fitted into it. The two are then crimped together to form a goodmechanical and electrical bond. Following this, the tube-wire joint isthen enclosed in an insulated sleeve which, in turn, is mounted betweena pair of metal sleeves. However, the manner in which this is doneprovides the desired protection of the joint against mechanical andelectrical breakdown, even under quite adverse conditions. An addedadvantage lies in the fact that the cost of such electrical connectorsis less than comparable prior art devices.

The novel features which are believed to be characteristic of theinvention, both as to its organization and method of operation, togetherwith further objects and advantages thereof, will be better understoodfrom the following description considered in connection with theaccompanying drawing in which an embodiment of the invention isillustrated by way of example. It is to be expressly understood,however, that the drawing is for the purpose of illustration anddescription only and is not intended as a definition of the limits ofthe invention.

FIGURE 1 is a view, partly in cross-section, of a heater element, theheater element representing one kind of device with which an electricalconnector according to the present invention may be used;

FIGURE 2 is a view of the same heater element but with electricalconnectors according to the present invention respectively mounted onits ends; and

FIGURE 3 is a cross-sectional view of the electrical connector andillustrates the manner in which wires of two different diameters may bejoined and the joint protected.

Considering now the features of the invention in detail, reference ismade to the drawing wherein like or similar parts or elements aresimilarly designated throughout the several figures. In FIG. 1, theheater element, generally designated 10, is in the form of a coil andincludes a relatively thin resistive wire 11 surrounding which is alayer 12 of suitable dielectric material, the dielectric layer itselfbeing covered over with a metal tubing or sheath 13. Stated ditferently,wire 11, layer 12 and sheath 13 are concentrically arranged, with thewire and sheath respectively being the inside and outside elements andthe insulation being located therebetween. Moreover, as will be notedfrom the figure, insulation 12 and sheath 13 have been stripped from theends of wire 11 so that the ends are exposed for a short distance forthe purpose of allowing connections to be made to them. It should alsobe noted that although the heater in FIG. 1 is in the shape of a coil,other configurations may at times also be involved. In other words, theshape of the heater element is not important insofar as the invention isconcerned.

Referring now to FIG. 2, a pair of electrical connectors, generallydesignated 14, are shown mounted on the ends of heater 10, the primarypurpose of the connectors being to firmly interconnect the ends of wire11 with external wires or leads 15. It will be noticed from FIG. 2 that,in accordance with the preferred arrangement of the connectors, thediameter of wires 15 are the same or substantially the same as thediameter of sheath 13.

For a detailed consideration of electrical connector 14, attention isdirected to FIG. 3 wherein an enlarged view of an electrical connector,partly in cross-section, is presented. As shown therein, external wireor lead 15 has a hole 15a bored in it, the hole starting at the end ofthe wire and extending along its axis for a short distance. The exposedor stripped end of wire 11 is inserted in hole 15a and, after this isdone, the end portion of wire 15 that surrounds the hole is crimped, asat 15b, thereby forming a firm mechanical and electrical bond with wire11.

Mounted over and, therefore, surrounding this juncture of wires 11 and15 is an insulative or dielectric sleeve or tube 16'which may, as anexample, be made of aluminum oxide (A1 0 Member 16 is rigid and,therefore, not only protects the wires electrically but also providessome measure of mechanical support to prevent the wires from bending. Inthis regard, it should be noticed that sleeve 16 fits over the wiressnugly, with the result that the wires are held firmly in position.Furthermore, as previously mentioned and as can now more clearly be seenfrom FIG. 3, the diameter of wire 15 is equal to the outer diameter ofsheath 13 covering wire 11.

Insulative sleeve 16 is itself mounted within a pair of metal sleeves17a and 17b which may, for example, be made of Kovar metal. Sleeves 17aand 17b fit quite tightly over sleeve 16. This, plus the fact thatsleeves 17a and 17b are extra thick where they cover insulative sleeve16, provides an air tight arrangement with the needed mechanical andelectrical protection, even under such adverse operating conditions asare found in a vacuum and at elevated temperatures. Lastly, as a finalbond or seal, sleeves 17a and 17b are crimped at their ends, as at 17c,the crimping being made possible by the fact that insulative sleeve 16does not extend fully through metal sleeves 17a and 17b. As a result, aspace 18 exists between sleeves 17a and 17b and wires 13 and 15 whichpermits this crimping to take place. However, the technique of brazingmay be used as a substitute for such crimping.

Although a particular arrangement of the invention has been illustratedabove by way of example, it is not intended that the invention belimited thereto. Accordingly, the invention should be considered toinclude any and all modifications, alterations or equivalentarrangements falling within the scope of the annexed claims.

Having thus described the invention, what is claimed 1. An electricalconnector combination comprising: a tubular-shaped electrical elementhaving a first wire extending from one end thereof, the diameter of saidelement being greater than the diameter of the wire extending therefrom;a second wire whose diameter is equal to the diameter of said electricalelement and which has a hole in it along its axis in which said firstwire is mounted to form a mechanical and electrical junctiontherebetween; a tubular-shaped insulative sleeve mounted on saidelectrical element and said second wire to iusulatingly cover saidjunction therebetween; and a pair of tubularshaped metal sleeves snuglymounted on said insulative sleeve and extending beyond the ends thereof,said insulative sleeves being spaced apart at their inner ends toprovide insulation therebetween and respectively bonded to said elementand said second wire at their outer ends.

2. An electrical connector combination comprising: an electricalconductor having a first wire, a layer of insulative materialsurrounding said first wire, and a metal sheath surrounding saidinsulative layer; a second wire whose diameter is equal to the diameterof said metal sheath and which has a hole in it along its axis in whichsaid first wire is mounted; an insulative sleeve mounted and extendingover said metal sheath and second wire, the diameter of said sleevebeing equal both to the diameter of said second wire and the diameter ofsaid metal sheath to provide a snug fit therebetween; a pair of metalsleeves mounted on said insulative sleeve and respectively extendingbeyond the ends thereof; and means for respectively bonding the ends ofsaid metal sleeves to said electrical conductor and said second wire.

References Cited by the Examiner UNITED STATES PATENTS 1,757,561 5/1930Emmons l74-85 2,272,282 2/ 1942 Wiegand 17477 3,122,718 2/1964 Boggs 338273 3,164,299 8/1964 Norton 174-88 3,230,298 l/1966 McOrlly 338-24 XLEWIS H. MYERS, Primary Examiner.

DARRELL L. CLAY, Examiner.

2. AN ELECTRICAL CONNECTOR COMBINATION COMPRISING: AN ELECTRICALCONDUCTOR HAVING A FIRST WIRE, A LAYER OF INSULATIVE MATERIALSURROUNDING SAID FIRST WIRE, AND A METAL SHEATH SURROUNDING SAIDINSULATIVE LAYER; A SECOND WIRE WHOSE DIAMETER IS EQUAL TO THE DIAMETEROF SAID METAL SHEATH AND WHICH HAS A HOLE IN IT ALONG ITS AXIS IN WHICHSAID FIRST WIRE IS MOUNTED; AN INSULATIVE SLEEVE MOUNTED AND EXTENDINGOVER SAID METAL SHEATH AND SECOND WIRE, THE DIAMETER OF SAID SLEEVEBEING EQUAL BOTH TO THE DIAMETER OF SAID SECOND WIRE AND THE DIAMETER OFSAID METAL SHEATH TO PROVIDE A SNUG FIT THEREBETWEEN; A PAIR OF METALSLEEVES MOUNTED ON SAID INSULATIVE SLEEVE AND RESPECTIVELY EXTENDINGBEYOND THE ENDS THEREOF; AND MEANS FOR RESPECTIVELY BONDING THE ENDS OFSAID METAL SLEEVES TO SAID ELECTRICAL CONDUCTOR AND SAID SECOND WIRE.